h1 {
  color: red;
}

body, html {
  margin: 0;
  padding: 0;
}
#main {
  margin: 50px auto;
  width: 260px;
}

#calc {
  margin-left: 36px;
  width: 60px;
}

input {
  margin: 5px 0;
}
span {
  color: red;
  margin-left:5px;
} 
#width-err,  #height-err {
  color: red;
  margin-left: 36px;
}
